Autumn shows signs of armyworms

Caroline Booth Lara | Oct 16, 2006

Fall has brought the return of armyworms to Texas and Oklahoma, with sightings of both fall and beet armyworm species in recent weeks. In order to combat these destructive pests in a timely way, producers must get out and scout their fields frequently.

“Fall armyworms will typically be seen on wheat, rye, small grains and even corn,” says James Locke, soil and crops specialist at the Noble Foundation in Ardmore, Okla. “Beet armyworms are more common in vegetable and cotton production, and I consider them to be more of a warm-season pest.

However, Locke says, he recently visited an operation in Atoka County, Okla., producing hard red winter wheat that had a serious beet armyworm problem.

“This four- to five-leaf stage wheat was infested with probably 90 percent beet armyworms to 10 percent fall armyworms, interestingly,” he says, adding that this might be due in part to the warm fall weather.

When scouting, Locke suggesting starting around field edges and looking for the “windowpaning” effect — a distinctive feature caused by young worms eating the surface off the leaf, but not consuming the entire structure.

“When you see that, get down on your hands and knees and look for worms feeding on the plant. If it is in the warmer part of the day, check the soil surface if you don’t see worms on the plants — they might be underneath dirt clods, hiding from the sun.”

Fall armyworms are distinguished by a light-colored inverted “Y” shape on their dark brown heads; beet armyworms typically are a light green color and have dark green or black spots on the second segment behind the head.

Locke says that three worms per square yard is the control threshold out in crop fields, while seven to 10 worms is the threshold on field borders or turn rows.

“Type and rate of control will be dependent on the type of armyworm you have, because beet armyworms are harder to kill,” Locke says. “My most frequent recommendations for control products are Lorsban, Warrior and Mustang Max.”